ASTM A767 - Galvanizing Steel Bars for Concrete Reinforcement - Rebar

ASTM A767, Standard Specification for Zinc-Coating (Galvanized) Steel Bars for Concrete Reinforcement first and foremost specifies the minimum mass (weight) of zinc coating on reinforcing steel bars by size. Number 12 and smaller bar must have a minimum of 3.0 oz./ft2 and Number 13 and larger bars must have a minimum of 3.5 oz/ft2. The specification also calls out specific recommended before galvanizing bending radii. This cold working of the bars causes induced stresses that may be released after the bars are immersed in the molten 850 F zinc bath. Unique to this specification is also the requirement the galvanized bars be immersed in a heated, sodium dichromate solution immediately after the process. This post-treatment helps to prevent the formation of wet storage stain on the bars when they are in bundles at a job site and also promotes good adhesion of the galvanized rebar to the concrete it is placed in. It is important to note reinforcing steel used in conjunction with structural steel, welded to a fabricated assembly is not governed by ASTM A767 but rather ASTM A123, the standard specification for zinc coatings on iron and steel products.

Comments

February 1, 2016

Alana Hochstein

Hi Hank,

Either Coating Class I or Class II are chosen by the customer depending on the corrosion protection requirements - Class II will provide a coating with less thickness. There are no guidelines concerning the use of Class 1 or Class 2 within the ASTM A767 document.

The most common method for the QC to measure coating thickness on reinforcing steel bar is by magnetic thickness gauge in accordance with ASTM E 376. The coating thickness for Class I in Table 1 of ASTM A767 is the minimum coating thickness required for acceptance.

February 1, 2016

HANK

Question: good day, I work in Taiwan as a sales person, L have a custom is asking for the standard ASTM A676 about the amount of zinc. Could you define the meaning of CLASSI and CLASSII. Normally after iron dig into zinc, how can the QC measure by the thickness. And depends on which standard and which level if I want to know how much the zinc contains. According to ASTM A767: class l SIZE NO,10 915 g/m2 and size no 13 and larger 1070g/m2 CLASSII size no13 and larger 610g/m2 ?